1. Field of the Disclosure
The present disclosure relates to connection arrangements for optical communications.
The disclosure was developed with specific attention paid to the possible use in connecting Optical Sub Assemblies (OSA's) and Electronic Sub Assemblies (ESA's) in optical communication devices such as e.g. transceivers for optical communications.
2. Discussion of the Background Art
Electro-optical communication devices such as transceivers for optical communications typically comprise an Electronic Sub Assembly (ESA) and an Optical Sub Assembly (OSA) in a single package. Such an arrangement is schematically illustrated in FIG. 1, where a carrier body 100, typically of a metal material, is shown having mounted thereon an Electronic Sub Assembly (ESA) 102 and an Optical Sub Assembly (OSA) 104. The Electronic Sub Assembly 102 is e.g. in the form of a small printed circuit board (PCB) 106 having electronic circuitry 108 mounted thereon. The Optical Sub Assembly 104 is typically in the form of a casing or enclosure mounted at the “distal” end 110 of the carrier body or package 100 of the transceiver where the optical components of the transceiver i.e. the laser diode (transmitter) and the photodetector (receiver) are arranged in view of connection to the optical link fibre(s).
A current trend in recent years is to make transceivers pluggable, possibly in the form of “hot” pluggable units, that is units that can be plugged/unplugged in a host system without powering-off the host system. Such an arrangement is exemplified in FIG. 1. There, the ESA illustrated is provided at its “proximal” end with slidable electrical contacts 112 that enable plugging/unplugging the transceiver in a sort of socket (not shown) provided in the rack where the transceiver is mounted.
Proper and effective connection between the OSA and the ESA is a critical issue in manufacturing optical transceivers, especially when operating rates of the order of 10 Gbit/s and higher are contemplated.
In the first place, the connection must be as short as possible in order to guarantee high data rates. Additionally, the connection should be not too rigid in order to avoid damages due to shocks or vibrations.
Assembling the OSA and the ESA in the transceiver package should be a simple, reliable process. The ESA and the OSA are tested separately (in order to circumvent yield problems related to malfunctioning of only one of the subassemblies) and then connected. After being assembled and connected, the ESA and the OSA are tested again in order to extract and verify the programming parameters and the functionality of the complete transceiver.
Assembling the OSA and the ESA is usually performed manually or by resorting to automated, dedicated soldering process that inevitably tend to be quite expensive.
FIG. 2 is an enlarged view of the portion of FIG. 1 indicated by arrow II and includes a portion M magnified for the sake of clarity of illustration. FIG. 2 is exemplary of conventional solutions where the connection of the OSA and the ESA is produced by (hand) soldering brazed leads of the OSA directly onto soldering pads carried by the ESA.
Specifically, the left-hand portion of FIG. 2 illustrates some of the components typically located within the OSA casing. By referring, by way of example, to the transmitter side, these include a laser diode 114 having associated focusing optics in the form of e.g. a “ball” lens 116. The laser source 114 is mounted onto a thermal conditioning element 118 such as a Peltier element.
While the transmitter side of the OSA is considered here by way of example, a substantially similar layout can be considered for the receiver side—insofar as the points of momentum for the disclosure are concerned. Additionally, while a transceiver is being primarily referred to, this description will almost identically apply to electro-optical communication devices including only a transmitter or a receiver.
As used herein, the wording “electro-optical communication device” is thus inclusive of any of an optical transmitter, an optical receiver and an optical transmitter/receiver (i.e. a “transceiver”).
The reference numeral 120 designates as a whole a “feedthrough”, namely a shaped body of a rigid material as required for high data rate operation—such as e.g. ceramics or glass that creates (via electrical conductive stripes provided thereon) electrical pathways through the OSA casing. Specifically, in the exemplary arrangement illustrated in FIG. 2, the feedthrough 120 is shown having a sort of pod-like formation 122 protruding from the OSA casing wall. One or more electrical leads 124 brazed on the upper side of the formation 122 extend from the OSA feedthrough 120 to be soldered to corresponding conductive pads (not visible) on the ESA thus ensuring electrical connection between the OSA and the ESA. Alternative prior art solutions may include, in the place of the lead or leads 124, a flexible printed circuit board, known also as a “flex”.
However effective, the prior art solutions discussed in the foregoing are costly and entail a number of disadvantages. In appreciating these negative factors, one must take into account the fact that the elements involved are generally very small: for instance, the ceramics/glass body comprising the feedthrough 120 may have a height and a length (as observed in FIG. 2) smaller than 5 mm, typically 3 mm or less.
On that size scale, leads such as the leads 124 may turn out to be too rigid, and measures have to be taken in order to improve resistance against shocks and vibrations. This requires design efforts, expensive profiling fixtures and making the leads longer than strictly required for connection purposes. However, longer leads included in the RF portion of the transceiver militate against high data throughput.
Using a “flex” (i.e. a flexible printed circuit board) somehow palliates the problems related to shock resistance. Unfortunately, using a flex renders the assembly process rather complicated, this being particularly the case if an automated production environment is considered. Additionally, in those optical communication devices where a very limited space is available, such as e.g. Small Form Factor Pluggable (SFP) transceivers, using a short flex is practically mandatory, and such a short flex tends to be as rigid as a fixed lead.
A particularly penalising feature of prior art arrangements as illustrated in FIG. 2 lies in that these arrangements involve a steady (i.e. non-releasable) connection between the OSA and the ESA e.g. by soldering. In the case of malfunctioning of either subassembly, the transceiver as a whole is usually disposed of: in fact, separating the malfunctioning subassembly from the subassembly that operates correctly, removing the malfunctioning subassembly from the transceiver, substituting a replacement unit for the malfunctioning subassembly removed and re-establishing the mechanical and electrical connections between the OSA and the ESA is an expensive and time-consuming process, and may also give rise to problems in terms of reliability. In turn, the OSA and ESA are both rather expensive components, and dispensing with transceiver—as a whole—because only one of the ESA and the OSA is malfunctioning is hardly an acceptable choice from the economical viewpoint.
The object of the present disclosure is thus to provide an arrangement that overcomes the drawbacks intrinsic to the prior arrangements considered in the foregoing.